The need to artificially introduce food into the gastrointestinal tracts of individuals who cannot eat, or will not eat, has been well known throughout and even prior to this century. Before the mid-1970's, feeding was done nasogastrically with red rubber or polyvinylchloride feeding tubes. The use of enteral feeding by means of nasogastric tubes expanded dramatically in the late 1970's with the introduction of tubes constructed of either silicone rubber or polyurethane. Being constructed of stronger materials, these tubes incorporated thinner walls, and were therefore smaller in outside diameter. These smaller tubes were easier to insert and more comfortable for the patient, and their introduction resulted in a very rapid growth of enteral nutrition via the nasogastric route, and increased interest in enteral nutrition in general.
By the 1980's problems with nasogastric feeding were recognized by clinicians and the advantages of direct gastrostomy access into the stomach through the abdominal wall had been described by Vazquez in U.S. Pat. No. 4,356,824, and by Moss in U.S. Pat. No. 4,543,085. Refinements in securing gastrostomy tubes in the patient were described by Parks in U.S. Pat. No. 4,666,433 and in U.S. Pat. No. 4,685,901.
The 1980's also saw the refinement of methods for forming the gastrostomy stoma. Prior to the 1980's, the stoma or gastrostomy was formed surgically by the Stamm procedure, which required a surgical laporatoratomy to insert the tube, usually a latex urologic Foley retention catheter. A new method, called a "PEG", or Percutaneous Endoscopic Gastrostomy, eliminated the need for a surgical gastrostomy to place the gastrostomy tube and dramatically expanded the interest in the use of direct gastrostomy tubes. The advantages of PEGs and the PEG technique were described by Quinn et al. in U.S. Pat. No. 4,795,430. The word "PEG" is used herein to identify both the tube and the procedure.
Gastrostomy tubes can generally be organized into three main groups, the third of which includes two subgroups:
1. SPECIALTY TUBES placed at the time of gastric surgery by the Stamm technique. The Moss and Vazquez patent tubes are examples of this type. PA1 2. PEG tubes which are used to form the initial stoma or gastrostomy. PA1 3. REPLACEMENT TUBES which are used to replace the PEG tube after a period of time because the PEG has worn out with use, or because a device which is more specific to the patient's need is required. These tubes are inserted into the original stoma created by either the PEG or the Stamm technique. They include: PA1 1. A tube to carry the enteral feeding formula into the stomach and/or the intestine. PA1 2. An outflow port in the distal end of the tube. The port or ports may be incorporated in the end or the side wall of the tube. They may also be incorporated in a separate, molded bolus fastened to the distal end of the tube. PA1 3. An administration set connector attached to the proximal end of the tube, which is outside of the patient. PA1 4. A distal end retention device to hold the tube in the stomach, e.g., an inflatable balloon or a molded retention shape which can be deformed with a stylet for insertion and removal. PA1 5. An external bolster to secure the tube at the point where it exits the skin. This bolster maintains the proper distance between the external bolster and the internal retention device, a distance corresponding to the combined thickness of the individual patient's skin, abdominal wall and stomach wall at the site of the gastrostomy. PA1 6. An anti-reflux valve to prevent leakage of gastric acids from the patient when the administration set is being changed or when violent coughing causes excessive back pressure. PA1 7. A measurement system to measure the patient's abdominal wall thickness so that the tube length between the retention device and the external bolster can be adjusted to match this thickness.
a. LOW PROFILE REPLACEMENT TUBES which are preferred for active patients who wish to conceal the tube's outer fitments during periods when they are not receiving feeding formula. The background for this type of replacement tube is described by Quinn et al. U.S. Pat. No. 5,125,897. PA2 b. SIMPLE REPLACEMENT tubes which are less complicated and less expensive and are used for patients who are not active and have no need to hide their device.
These devices are direct modifications of the original urologic Foley catheters used in early gastrostomies. They are described by Parks in U.S. Pat. No. 4,666,433.
With some exceptions within individual designs, gastrostomy tubes, or tube assemblies (as they will hereinafter be referred to) of the aforedescribed types each incorporate the following seven features or components:
Just as gastrostomy tube assemblies are used for enteral feeding, so suprapubic catheter tube assemblies are used to administer drugs to, or drain urine from, the bladder. Such tube assemblies comprise the same seven features or components referred to above in the context of gastronomy tube assemblies. However, they access the bladder through a stoma formed in the abdominal wall above the bladder or pubic area.
Insofar as the construction and operation of the tube segments for such PEG tube assemblies, replacement gastrostomy tube assemblies and suprapubic catheter tube assemblies are concerned, silicone and polyurethane are the materials of choice. Silicone is softer and more compliant than polyurethane. Silicone has a lower modulus of elasticity than urethane. Softness is desirable in medical catheters. However, softness also increases the ability of tube segments to kink and collapse, which are undesirable characteristics. These problems have heretofore normally been addressed by making the silicone rubber walls of the tube segments thicker or by constructing the tube segments from stronger, but less flexible, polyurethane. The designer usually has had to make a choice between a smaller, but less flexible, urethane tube segment and a larger, softer silicone tube segment.
Silicone tube segments including coil springs embedded in the silicone to prevent wall collapse have been used for endotracheal tubes. The use of a coil spring embedded in a silicone rubber wall in such tube segments has served to prevent their collapse, even where relatively soft silicone rubber has been used. For example, in one known instance, a silicone rubber endotracheal tube segment having a wall thickness of as low as 0.075 inches and a Durometer hardness reading of as low as 35A (a discussion of durometer hardness measurements is included in the following description) has been used.
Flexibility and resistance to kinking, as well as resistance to collapsing, are characteristics which are particularly important in gastrostomy and suprapubic catheterization tube segments. Because these tube segments exit the body perpendicular to the skin, it is desirable to be able to bend them to a right angle so that they can lie next to the skin. This problem is addressed in Quinn et al. U.S. Pat. No. 4,834,712. In addition, some forms of gastrostomy tube segments include extensions which feed out of the stomach into the duodenum or jejunum. These tube segment extensions must be able to negotiate from one to five acute angle turns, depending whether they are placed in the duodenum or further into the jejunum. Tube segments with a higher modulus, i.e., less flexible, can dig into the side walls of the intestine and resist making the required tight turns as they move through the intestine.